1. Field of the Invention
The present invention relates to a system for connecting two substantially tubular members, particularly two ferrules of an axial compressor case.
2. Description of the Related Art
Axial compressors, for example, in turbojets, are generally made of an axial sequence of rotors and stators. Each rotor is a set of rotary blades secured to the driving shaft of the compressor. Each stator is a set of stationary rectifying vanes secured to the compressor case. Each rotor is followed by a stator, so as to form a compressor stage.
A turbojet can comprise a plurality of successive compressors, for example, a low pressure compressor mounted in front of a high pressure compressor, wherein each comprises a different driving shaft.
Generally, an axial compressor case is formed by a set of substantially tubular members, also called ferrules, successively connected. Each ferrule generally surrounds a compressor stage, i.e. a rotor and a stator A ferrule will thus normally comprise the set of stationary vanes forming the stator, or means for securing said stationary vanes, as well as a abradable inner surface so as to avoid an excessive friction with the rotor blades.
The pairs of successive ferrules are connected via connecting means comprising:                a) two flanges, each being substantially annular and comprising a proximal face intended to be integral with one of both successive ferrules and a distal face, and        b) securing members for pressing the distal faces of both flanges one against the other, so as to be able to transmit tensile and compression axial stresses between both flanges.        
As used herein, distal face means the most remote face of the ferrule body, whereas proximal face means the nearest one of the ferrule body. In the state of the art, there are used as securing members bolts crossing holes provided in the flanges. However, such an arrangement has several inconvenients.
Should one of the compressor blade or vane break, significant circumferential stresses will become added to the axial and radial stresses between the pairs of adjacent ferrules. Such stresses have a shearing effect on the bolts of the connecting system, requiring the use of a large number of bolts with a considerable diameter for connecting ferrules. With the aim to solve the problem of the too numerous bolts, it is necessary to oversize the flanges by increasing the external diameter.
In addition to the cost and weight inconvenients resulting from such an oversizing, the radial bulk of enlarged flanges also results in other problems. So, in numerous applications, such a bulk makes the assembling and disassembling operations difficult, because of interferences between flanges and members outside the compressor, such as, for example, hoods. More particularly, in the field of turbojets, it could be desirable to be able to disassemble the low pressure compressor at the rear in order to make the maintenance easier. However, if the connecting flanges of the ferrules of the compressor case are too bulky, they will abut against the intermediate case, generally provided at the back of the low pressure compressor and used for supporting the whole turbojet.
This invention has also the object of overcoming the inconvenients of the state of the art providing a system for connecting tubular members allowing to minimise the radial bulk of such a system, particularly in the case of ferrules of an axial compressor case.